Coke formation in furnace tubes in ethane cracking processes

乙烯生产商在烃类蒸汽裂解装置中由于焦炭的形成而造成反应器管的污染，造成了巨大的产量、效率和经济损失。焦炭在炉管中的堆积增加了炉管间的压降，减少了向炉管内流动的气体传递的热量。当压力降或炉膛热负荷达到临界值时，乙烷-蒸汽裂解过程必须停止，炉管中的焦炭必须排出。脱焦通常每30-90天进行一次，每个乙烷裂解装置在甲板或非生产模式下的时间高达15%。因此，了解和减少炉管中的焦炭形成对乙烯制造商非常重要；操作上和经济上。我们的工作集中在三个关键领域：了解工厂操作条件如何影响控制反应副产物转化为焦炭的气相动力学，将这些结果与实验室规模的模拟焦化研究相关联，并采用详细的焦炭表征研究来了解工厂操作条件，特别是乙烷蒸汽进料中的成分如何影响焦炭的性质。在这项工作中需要研究的重要变量包括温度、乙烷-蒸汽在热区停留时间、蒸汽和硫含量以及基材表面的性质。现有的最先进的研究工具，结合在过去三年的合作工作中开发的广泛知识，将用于实现这些目标。在这项工作的过程中，两名研究助理和两名研究生将在这个项目下接受培训，并将准备加入加拿大的工业和学术队伍。从这项工作中获得的知识和专业知识将转移给我们的工业合作伙伴NOVA Chemicals，因此它可以用作不同工厂操作条件如何影响焦化速率的预测模型。这种对碳氢蒸汽裂解过程的新认识也将为阿尔伯塔省和加拿大其他存在焦化问题的蒸汽石化过程带来更广泛的好处。

Ethylene producers suffer from huge production, efficiency and economic losses due to fouling of the reactor tubes by coke formation in their hydrocarbon-steam cracking units. The accumulation of coke in the furnace tubes increases the pressure drop across the tubes and reduces the heat transfer to the gases flowing in the tubes. When either the pressure drop or the furnace heat load reaches a critical value, the ethane-steam cracking process has to be stopped and the coke in the furnace tubes has to be removed. Decoking is typically performed every 30-90 days and each ethane cracker is in the decking or non-production mode for up to 15% of the time. Hence, understanding and reducing the coke formation in the furnace tubes is very important to ethylene manufacturers; operationally and economically. Our work centers on three key areas: understanding how plant operating conditions influences the gas-phase kinetics that control conversion of reaction by-products to coke, correlating these results to lab-scale simulated coking studies, and employing detailed coke characterization studies to understand how plant operating conditions, and particularly components in the ethane-steam feed, impact the properties of the coke. Important variables to be studied in this work include temperature, ethane-steam residence time in the hot zone, steam and sulfur content, and nature of the substrate surface. Existing state-of-the-art research tools combined with extensive knowledge developed over three years of previous collaborative work will be used to reach these goals. Over the course of this work, two research associates and two graduate students will be trained under this project and will be ready to join the Canadian industrial and academic workforce. The knowledge and expertise gained from this work will be transferred to our industrial partner, NOVA Chemicals, so that it can be used as a predictive model of how different plant operating conditions will impact coking rates. This new understanding of hydrocarbon-steam cracking process will also have a broader benefit for other steam-based petrochemical processes within Alberta and Canada where coking is a problem.